Hi,

When you want to express concentration of solution

or

The quantity that defined as the ratio between the amount of component to the total component in solution 

Example - A &  B forming a solution that is AB

A + B --> AB 

so how will you calculate moles fraction of A only

Mole fraction (X_A) = Mole of A / total mole fration of component  

Thanks for asking

Good day :)